Cellular uptake induced biotoxicity of surface-modified CdSe quantum dots
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Cellular uptake of quantum dots (QDs) by cells is of utmost importance for establishing QDs as biostable fluorescent markers that facilitate early diagnosis and detection of cancer. The surface states of QDs are critical to enhance the cellular uptake. Biocompatible CDSe QDs were synthesized using mercaptopropionic acid, amino-ethanethiol HCl, cyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetrabutylammonium iodide (TBAI), and sodium dodecyl sulfate were functionalized using ligand-exchange method. Cytocompatibility and cellular uptake of QDs were evaluated in human embryonic kidney cells (HEK-29), and breast cancer cells (MCF-7) as reduced cytotoxicity is desirable for biological applications. Approximately, 60 % cytotoxicity was observed in all surface-coated QDs and QD100 in 72 h in both the cell lines, except TBAI that indicated 30 % cytotoxicity in 72 h, and only 10 % in 24 h. Glutathione, the detoxifying molecule, is detrimental for understanding the oxidative stress of the cell. The QDs showed enhanced Glutathione-S-transferase (GST) activity in the MCF-7 cell line. In HEK, CdSe per se was also able to induce a high level of GST. QDs toxicity may either be related to the induction of reactive oxygen species or the direct release of metal ions. Optimization of QDs in terms of quantification and DNA damage is imperative for realistic biological applications.
KeywordsQuantum dots Cellular uptake Oxidative stress GST Cytotoxicity Drug delivery Health effects
SS acknowledges University Grants Commission, Government of India for a research fellowship. KR acknowledges receipt of senior research fellowship from Council of Scientific and Industrial Research, Government of India. M. Pal is thankful to Department of Biotechnology for Senior Research Fellowship.
Conflict of interest
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